Aprepitant, the chemical name of 5-[[(2R,3S)-2-[(R)-1-[3,5-bis(trifluoromethylphenyl)ethoxy]-3-(4-fluorophenyl)-4-morpholin yl]methyl]-1,2-dihydro-3H-1,2,4-triazol-3-one, has the structure of Formula V:

Aprepitant is the first neurokinin-1 (NK-1) receptor antagonist developed by Merck Company, USA. This medicine can pass through the blood brain barrier, and antagonize NK-1 receptor with high selectivity, so as to block the effect of substance P, and additionally, it has lower affinity to NK-2 and NK-3. Aprepitant is clinically used for the prevention of nausea and vomiting due to chemotherapy, as well as postoperative nausea and vomiting. Aprepitant was marketed in 2003 under the trade name of Emend.
In the synthetic route reported by Karel M. J. Brands et al. in J. AM. CHEM. SOC. 2003, 125, 2129-2135, the compound of Formula VII is an important intermediate, which can be synthesized by the condensation reaction of aqueous glyoxalic acid solution and the compound of Formula VI as the starting material, which has the following reaction equation:

Additionally, another preparation method for the compound of Formula VII was also reported by Todd D. Nelson in Tetrahedron Letters 45 (2004) 8917-8920. In this method, the compound of Formula VII was obtained by reducing the compound of Formula VIII using lithium tri-sec-butylborohydride, in which the compound of Formula VIII was obtained by the reaction of the compound of Formula VI and diethyl oxalate. However, the yield of this method is low, and the reducing agent lithium tri-sec-butylborohydride is demanded, which is inflammable, corrosive and expensive, so that this is not favorable for industrial production.

In the present invention, 4-substituent-2-hydroxymorpholin-3-one is obtained by the condensation reaction of aqueous glyoxalic acid solution and the compound of Formula IV as the starting material. Especially, when electron-withdrawing substituents are bonded to the benzene ring, the yield of 4-substituent-2-hydroxymorpholin-3-one can be enhanced significantly.